STAT1/3 And ERK1/2 Synergistically Regulate The Proliferation And Collagen Synthesis On CFs Induced By High Glucose

Background:Hyperglycemia or high glucose(HG), a manifestation of diabetes mellitus,causes cardiomyopathy leading to heart failure. Cardiac fibrosis is one of the major pathological processes of diabetic cardiomyopathy, primarily by causing excessive accumulation of collagen within the interstices of the myocardium, which can result in impaired diastolic and systolic functions. Treatment of cultured CFs with high concentrations of glucose(HG) results in increased proliferation of CFs and collagen synthesis. However, the molecular mechanisms underlying the effects of HG on CF function, including proliferation and collagen synthesis, are not completely understood. STATs belong to an intracellular transcription factor family that primarily mediate cytokine- and growth factor-induced signals that are activated by diverse biological responses including proliferation, differentiation and apoptosis. The STAT signaling pathway has been shown to be an integral part of the responses of the myocardium to various cardiac insults. The STAT pathway also has been documented to take a part in the pathogenesis of liver fibrosis, pulmonary fibrosis and renal fibrosis, as an especially important mechanism for renal fibrosis by which hyperglycemia contributes to renal damage. These results predict that STAT may have a role in the process of myocardial fibrosis induced by HG. We hypothesized that HG stimulates STAT phosphorylation, and ERK1/2 and STAT cooperatively promote collagen synthesis in CFs through a crosstalk mechanism. The present study was designed to test this hypothesis by investigating whether the STAT and MAPK signaling pathways have synergetic effects on HG-induced proliferation and collagen synthesis in CFs. And thus may be new targets for the treatment of the pathogenesis of diabetic cardiomyopathy.Objective:The objectives of the present study were to determine whether the STAT proteins has a functional role in high glucose-induced proliferation of CFs and collagen synthesis in vitro and whether the STAT signaling pathway and ERK1/2 signaling pathway have synergetical effects on high glucose-mediated cardiac fibroblasts proliferation and collagen synthesis.Methods : Rat CFs were cultured in Dulbecco’s modified Eagle’s medium,supplemented with 5.5 or 25 mmol?L D-glucose, in the presence of absence of STAT1 inhibitor Fludarabine, STAT3 inhibitor S31-201 and ERK1/2 inhibitor PD98059. Proliferation were measured by the 3-(4,5-dimethyl-2 thiazoyl)- 2,5-diphenyl-2Htetrazolium bromide(MTT) assay, the production of Type I and III collagen was evaluated using real-time quantitative RT-PCR and ELISA, and the phosphorylation expression of STAT1 and STAT3 were analyzed by Western blot.Results:High glucose treatment promoted the proliferation of cardiac fibroblasts and collagen types I and III synthesis. High glucose treatment induced STAT1 and STAT3 phosphorylation in cardiac fibroblasts, the mode and level of STAT1 and STAT3 phosphorylation were significantly different. Fludarabine and S31-201 could both inhibited high glucose stimulated proliferation of cardiac fibroblasts and collagen types I and III synthesis with different effects. Combination of Fludarabine and PD98059 or combination of S31-201 and PD98059 both exhibited stronger inhibitions on proliferation of cardiac fibroblasts and collagen types I synthesis, but the effects and functional modes are different.Conclusions:Both STAT1 and STAT3 mediate the proliferation of cardiac fibroblasts and collagen synthesis induced by high glucose. STAT1 and STAT3 both have synergetic effects with ERK1/2 on regulating proliferation of cardiac fibroblasts and collagen types I synthesis.